Security systems that are designed to create a barrier against unauthorized persons entering dwellings or enclosed areas such as, homes, offices, places of business, fenced properties and the like are common. The typical security systems architectures are referred to as stand alone systems, some times also referred to as off-line systems, and host-based, real time systems. Stand alone systems provide access decisions via, a self contained electrical or electronic control module with connected to a data entry device. host-based, real time systems Typical data entry devices include keypads and proximity, magnetic strip or biometric readers. Once the information provided by the entry device is verified by the control module an electrical or electronic signal is transmitted to power controlled door locks, allowing entry. The stand alone systems may also include exit control devices, such as request to exit (REX) systems, door open status detectors, movement or occupancy sensors and local door alarm output and may hard wired connections, wireless communication arrangements or a combination thereof.
With reference to FIG. 1, a host based, real time security system 100 comprises application software, one or more a controllers 104, and one or more user identification entry devices 106. The application software resides on a host computer 102, such as a server located at a host site, that is in electronic communication with the controller at the protected site. The application software provides user interfaces with the controller to provide access data parameters, alarm monitoring and output control. Other functions that can be provided by the application software include photo badging, video display and management, graphical alarm displays, visitor control, etc. The data is sent from the host to the controllers via the controller communication network 108. The controller or controllers 104 are installed adjacent to or in the vicinity of the access point being controlled, such an entry latching mechanism 109, where it is further connected to the data input device, such as a card reader or other means to identify the user. The controller has limited intelligence and is configured to make and execute decisions based upon user access information previously supplied to the system. The user provides the appropriate access information to data reader 102 at the entry point which transmits the user identification information to the controller 104 for an access authorization decision. Based on authorization parameters of the cardholder within the controller 104, access is granted or denied and access management processed accordingly.
Referring to FIG. 2 a host system is shown with a master controller 110 and two sub controllers 112. The master controller 110 is an intelligent controller with database information necessary for the system to make access and security decisions for the sub controllers 112. Each sub controller 112 is connected to user ID and entry control devices 106 such as a card reader, door lock control, request to exit, door status and other input and output controls connected directly to the sub controller 112. The user's entry data fed to the entry control device 106 is transmitted to the sub-controller 112. The identification information is than re-transmitted from the sub-controller to the master controller 110 for an access authorization decision. Based upon authorization parameters within the master controller 110 instructions regarding access grant or denial is sent from the master controller to the sub-controller 112 which then implements the instructions regarding entry.
In either architecture, the Host system disseminates access control, door management, alarm monitoring, sense input monitoring, and output control parameters to the various controllers via a secured communication network.
Although current systems are popular and extensively used a major deficient of these systems is that a failure in communication between system components, or a failure of either the master controller 110 or a sub-controller 112 translates to a failure of the system with respect to the components controlled by the failed controller. The failure of a master controller 110 is a single point of failure in the system, resulting in a failure of all sub-controllers 112 assigned to the failed master controller. A need in the industry exists for a fault tolerant security system architecture that eliminates the denial of access as a result of a single point of failure. A further need exists for a system which is configured to automatically recover from a failure. A still further need exists for a security system with redundancy so that when there is a single failure in the system a non-failed controller can automatically assume the tasks of a failed controller.